Compact bone is a structured material, one function of which in the body is to support mechanical loads. Generalized continuum theories for mechanical behavior are available, which are intended to describe structured materials. On the basis of its structure, we have advanced the hypothesis that compact bone obeys a generalized continuum theory, couple-stress elasticity theory, rather than classical elasticity which is usually assumed to hold. Experiments performed in quasistatic bending, quasistatic torsion, and torsion resonance disclose size effects consistent with couple-stress elasticity but inconsistent with classical elasticity. Nonclassical effects are sufficiently large that they may significantly perturb stress concentration factors around screw holes a few millimeters in diameter and modify stress distributions near orthopaedic implants. Future work will be directed toward measuring the several nonclassical elastic constants and experimentally studying actual strain fields near interfaces in bone. The aim is to correctly predict stress and strain fields in situations of importance in orthopaedic surgery.